Adsorptive separation is applied to the recovery of a variety of hydrocarbon and other chemical products. Chemical separations using this approach include: the separation of mixtures of aromatics into specific aromatic isomers, the separation of linear from nonlinear aliphatic and olefinic hydrocarbons, the separation of either paraffins or aromatics from a feed mixture comprising both aromatics and paraffins, the separation of chiral compounds for use in pharmaceuticals and fine chemicals, the separation of oxygenates such as alcohols and ethers, and the separation of carbohydrates such as sugars.
Packed beds of adsorbent materials are typically used in adsorption processes. Adsorbent materials are generally in the form of spherical beads, or pellets. Adsorbent materials are typically oxygen-containing compounds, carbon-containing compounds, or polymer-based compounds. Oxygen-containing compounds can be, for example, hydrophilic and polar, including materials such as silica gel and zeolites. Carbon-based compounds can be, for example, hydrophobic and non-polar, including materials such as activated carbon and graphite. Polymer-based compounds can be, for example, polar or non-polar functional groups in a porous polymer matrix.
In operation, a process stream is introduced into an adsorption bed, and the adsorbent material contained therein removes a desired or undesired component from the stream as it filters through the adsorption bed. After a given time period, the adsorbent material becomes saturated with the sorbate, and the adsorption process in that adsorption bed must be stopped in order to regenerate the adsorbent and remove the sorbate. After a regeneration cycle is complete, a new adsorption cycle can begin. Adsorption processes often operate in a swing bed arrangement so that one or more beds are active, and one or more beds are being regenerated.
Several problems can occur during operation with a swing bed arrangement. First, feed can be lost when switching a bed from active state to regeneration. In addition, there is a risk that when the adsorption bed is full, some of the material which is supposed to be adsorbed in the adsorption bed will flow through the adsorption bed and not be captured.
Thus, there exists a need for an improved method for operating an adsorption separation zone.